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copied!<p><strong>Caching is Key</strong></p> <p>As the others have said, you've got to use caching since you are performing repetitive disk I/O on data that doesn't change often.</p> <p>My example creates and caches a <code>List<T></code> of the image file paths you will need for each subsequent request. <code>System.Web.Caching</code> is perfect for this because you can create a <code>CacheDependency</code> object directly on your image directory -- if a file gets changed or added, your cache is automatically invalidated. It is then recreated the next time it is requested.</p> <p><strong>Avoiding Duplicates with the <code>HashSet<T></code></strong></p> <p>I bet you don't want two of the same pictures ever showing up in your header!</p> <p>Randomizing using <code>Random.Next</code> does not exclude previously generated duplicates. I used a <code>HashSet<T></code> as a poor man's unique randomizer since the <code>HashSet<T></code> will only allow you to add unique values.</p> <p><strong>The Model</strong></p> <p>This operation should be part of your model in MVC. You change it to go along with your other data fetching classes as you see fit.</p> <pre><code>using System; using System.Collections.Generic; using System.IO; using System.Linq; using System.Web; using System.Web.Caching; public class RandomImage { public static string[] GetImages(string folder, int count) { HttpContext context = HttpContext.Current; string virtualFolderPath = string.Format("/content/{0}/", folder); string absoluteFolderPath = context.Server.MapPath(virtualFolderPath); Cache cache = context.Cache; var images = cache[folder + "_images"] as List<string>; // cache string array if it does not exist if (images == null) { var di = new DirectoryInfo(absoluteFolderPath); images = (from fi in di.GetFiles() where fi.Extension.ToLower() == ".jpg" || fi.Extension.ToLower() == ".gif" select string.Format("{0}{1}", virtualFolderPath, fi.Name)) .ToList(); // create cach dependency on image randomFolderName cache.Insert(folder + "_images", images, new CacheDependency(absoluteFolderPath)); } Random random = new Random(); var imageSet = new HashSet<string>(); if (count > images.Count()) { throw new ArgumentOutOfRangeException("count"); } while (imageSet.Count() < count) { //using an hashset will ensure a random set with unique values. imageSet.Add(images[random.Next(count)]); } return imageSet.ToArray(); } } </code></pre> <p><strong>The Controller</strong></p> <p>Access the method in your controller something like....</p> <pre><code>string[] images = Models.RandomImage.GetImages("myPictures", 4); </code></pre>

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